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James Acton

@nuclear-jim.bsky.social
2.2K followers 56 following 235 posts

Co-director of the Nuclear Policy Program at the Carnegie Endowment For International Peace. I spend a lot of time thinking about nuclear weapons, advanced nonnuclear technology, and escalation.

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Reposted by James Acton
James Cameron @jjjcameron.bsky.social · 12/03/2026
Happy to contribute a 200-word take to this @carnegieeurope.bsky.social panel on France's nuclear strategy of "forward deterrence." Feat. @mgmessmer.bsky.social, @paulvanhooft.bsky.social, @drfranksauer.bsky.social, @hfayet.bsky.social, @laurensukin.bsky.social, @nuclear-jim.bsky.social, & more.
carnegieendowment.org
Taking the Pulse: Is France’s New Nuclear Doctrine Ambitious Enough?
French President Emmanuel Macron has unveiled his country’s new nuclear doctrine. Are the changes he has made enough to reassure France’s European partners in the current geopolitical context?
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James Acton @nuclear-jim.bsky.social · 25/11/2025
I'm thrilled to have a contract with @academic.oup.com for my book on "Entanglement and Unintended Escalation." (There'll be a better title!) The manuscript is drafted and currently being revised. Hopefully should be out second half of next year!
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Reposted by James Acton
Carnegie Endowment @carnegieendowment.org · 06/11/2025
Testing nuclear weapons by detonating warheads is like “nuking yourself in the foot,” writes @nuclear-jim.bsky.social. Trump can stop nuclear anarchy by testing in ways that don’t spark a global arms race or give away the U.S.’s data advantage. More here: carnegieendowment.org/emissary/202...
carnegieendowment.org
Trump Has an Out on Nuclear Testing. He Should Take It.
Sometimes good policy can be as simple as not nuking yourself in the foot.
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James Acton @nuclear-jim.bsky.social · 06/11/2025
Let's not nuke ourselves in the foot! I explain why it's so difficult to know if China and Russia are conducting ultra-low yield tests and why, even if they are, it's not in U.S. interests to restart testing. @carnegieendowment.org @carnegienpp.bsky.social carnegieendowment.org/emissary/202...
carnegieendowment.org
Trump Has an Out on Nuclear Testing. He Should Take It.
Sometimes good policy can be as simple as not nuking yourself in the foot.
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James Acton @nuclear-jim.bsky.social · 05/11/2025
I am entirely indifferent whether, in the event of a nuclear war, I am incinerated by a nuclear warhead delivered by a "traditional" ICBM, a hypersonic glider, a nuclear-powered cruise missile, or a nuclear-powered torpedo. All seem equally suboptimal to me.
media.tenor.com
elmo from sesame street standing in front of a wall
ALT: elmo from sesame street standing in front of a wall
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James Acton @nuclear-jim.bsky.social · 30/10/2025
¯\_(ツ)_/¯
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James Acton @nuclear-jim.bsky.social · 30/09/2025
The End of MAD? Join me, Steve Fetter, @jaysankarans.bsky.social, TD MacDonald, Ton Stefanik, @lauraegrego.bsky.social, @fiona-cunningham.bsky.social, and Charlie Glaser to discuss whether technological developments are undermining mutually assured destruction. Link for virtual rego in next post.
media.tenor.com
a man in a shirt and tie is screaming with his hands in the air .
ALT: a man in a shirt and tie is screaming with his hands in the air .
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Reposted by James Acton
Carnegie Endowment @carnegieendowment.org · 13/08/2025
What exactly is the government hiding in Tucson? Not much, says @nuclear-jim.bsky.social. He got an interesting souvenir there, regardless. See the first installment of Carnegie Office Hours for more treasures from James (if not nuclear secrets) here: buff.ly/dlUzF6n
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James Acton @nuclear-jim.bsky.social · 01/08/2025
I feel pretty strongly the @nytimes.com has the wrong framing here. This isn't serious; it's pathetic. I'd suggest something like: "Trump throws social media hissy fit invoking nukes after public spat with ex-president of Russia."
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James Acton @nuclear-jim.bsky.social · 01/08/2025
As much as I deplore nuclear signaling by tweet--can't believe I just wrote that--I would NOT necessarily assume there's a been change to the US nuclear posture. The U.S. always keeps ~4/5 SSBNs at sea ready to fire.
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James Acton @nuclear-jim.bsky.social · 01/08/2025
Ahem (Deleted earlier version, which was missing caption!)
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James Acton @nuclear-jim.bsky.social · 31/07/2025
Ah, yes, that crucial ninth significant figure...
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James Acton @nuclear-jim.bsky.social · 29/07/2025
Good gracious, Ignatius! Why I disagree with the normally excellent David Ignatius; recent oped on Iran.
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James Acton @nuclear-jim.bsky.social · 29/07/2025
The case for attacking Iran relied on emphasizing its technical prowess. The case that strikes were successful requires claiming that Iran is technically incompetent. foreignpolicy.com/2025/07/25/i...
foreignpolicy.com
There’s More Than One Way to Build a Bomb
Iran doesn’t need to rebuild its damaged facilities to sprint for a nuclear weapon.
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James Acton @nuclear-jim.bsky.social · 28/07/2025
On Friday, I argued in @foreignpolicy.com that Trump admin claims it had set Iran back by "years" were true but disingenuous. The same day, the normally excellent David Ignatius amplified the misleading U.S. and Israeli narrative. www.washingtonpost.com/opinions/202... Let's take a look... (1/n)
washingtonpost.com
Opinion | The 12 days that turned back the clock on Iran’s nuclear program
Israeli and American assessments agree Tehran’s infrastructure to finish a bomb is shattered.
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James Acton @nuclear-jim.bsky.social · 27/07/2025
🎶When you attend a funeral, It is sad to think that sooner orl… …ater, those you love will do the same for you. And you may have found it tragic, Not to mention other adjec.. …tives to think of all the weeping they will do. 🎶 RIP, Mr Lehrer.
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James Acton @nuclear-jim.bsky.social · 25/07/2025
Me in @foreignpolicy.com. The Trump administration's claim that Iran would need "years" to rebuild its previous nuclear program is like asserting that an unlocked bank vault would be impervious to a cyberattack. It’s true but misses the point. foreignpolicy.com/2025/07/25/i...
foreignpolicy.com
There’s More Than One Way to Build a Bomb
Iran doesn’t need to rebuild its damaged facilities to sprint for a nuclear weapon.
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Reposted by James Acton
Matthew Gault @mjgault.bsky.social · 24/07/2025
had @nuclear-jim.bsky.social on Angry Planet to explain what the current nuclear arm's race looks like. It's bad! He's got a solution that sounds radical, but is more palatable than living in a world where everyone is spending billions to construct more nukes
angryplanetpod.com
How Many Nukes Does It Take to Win a War? (Trick Question)
The world is living with a Cold War hangover.
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James Acton @nuclear-jim.bsky.social · 21/07/2025
🧵How much damage was done to Iran's nuclear program? An analysis of Friday's reporting of the U.S. government assessment. I'll focus on the @nytimes.com, which was clearer than the earlier but confused @nbcnews.com story. (1/n) www.nytimes.com/2025/07/17/u...
nytimes.com
New Assessment Finds Site at Focus of U.S. Strikes in Iran Badly Damaged
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James Acton @nuclear-jim.bsky.social · 11/07/2025
I can think of no reason at all why Iranian leaders won’t jump at the chance to follow the “Libya model.” Can you, Muammar?
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Reposted by James Acton
Hans Kristensen @nukestrat.bsky.social · 11/07/2025
Important piece from @nuclear-jim.bsky.social about how to develop a better nuclear deterrence posture. www.cfr.org/report/optim... James’ deep thinking on these matters is desperately needed at a time when deterrence debate at times sounds more like Cold War grab-bag posturing on autopilot.
cfr.org
Optimal Deterrence
The United States faces growing dangers of nuclear escalation, a new arms race, and proliferation. This report recommends an improved strategy for “optimal deterrence” and a path to rebuilding relati…
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James Acton @nuclear-jim.bsky.social · 10/07/2025
Personally, I'm open to all three possibilities--that all, some, or none of the HEU was moved pre-war. I simply don't know and there appears to be real disagreement among intel agencies here.
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James Acton @nuclear-jim.bsky.social · 10/07/2025
It'd be a pretty catastrophic outcome *IF* the attacks on Fordow failed to destroy centrifuges and they can be put back into service. I'm not claiming this is the case, but U.S. officials seem to be hinting it's a possibility. (1/n) @hugolowell.bsky.social
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James Acton @nuclear-jim.bsky.social · 09/07/2025
lol
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James Acton @nuclear-jim.bsky.social · 09/07/2025
🧵Introducing optimal deterrence. Here's my proposed U.S. nuclear strategy for managing escalation, arms racing, and proliferation with two nuclear peers, published through @cfr.org. Health warning: If you like counterforce, take a DEEP breath before reading on. (1/n) www.cfr.org/report/optim...
cfr.org
Optimal Deterrence
The United States faces growing dangers of nuclear escalation, a new arms race, and proliferation. This report recommends an improved strategy for “optimal deterrence” and a path to rebuilding relati…
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James Acton @nuclear-jim.bsky.social · 02/07/2025
My friend, Joshua Pollack, penned this beautiful and wry double obituary of his father, Jonathan Pollack, and his first boss, Barry Blechman. www.armscontrolwonk.com/archive/1220...
armscontrolwonk.com
Recalling two mentors
1. Jonathan D. Pollack My father, Jonathan Pollack, died at the end of May after what’s politely called a long convalescence. He had worked over several [...]
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Reposted by James Acton
Richard Nephew @richardmnephew.bsky.social · 02/07/2025
This.
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James Acton @nuclear-jim.bsky.social · 02/07/2025
The administration has argued that the destruction of Iran's uranium metal production lines at Isfahan will set its nuclear-weapon program back by "years." At Arms Control Wonk, I argue it may not even set Tehran back by months. www.armscontrolwonk.com/archive/1220...
armscontrolwonk.com
Guest Post: Sorry, Mr. Secretary, producing uranium metal isn’t particularly difficult
This guest post is by Dr. James M. Acton Central to the Trump administration’s case for the effectiveness of its air strikes on Iran is the destruction of [...]
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Ankit Panda @nktpnd.bsky.social · 29/06/2025
In today's @financialtimes.com, I reflect on the implications of the joint Israeli-US attacks on Iran for a fragile and bruised nonproliferation regime on.ft.com/45Jehd3
on.ft.com
Iran attack could be the death knell for nuclear non-proliferation
More countries will seek atomic weapons unless Europe and its allies defend a flawed but vital treaty
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James Acton @nuclear-jim.bsky.social · 29/06/2025
Then: We must go to war with Iran to deny it enrichment. Weaponization is too easy to be a useful barrier to proliferation. Now: Meh. It’s not a biggie that Iran has retained its HEU and centrifuge components. Weaponization is a major bottleneck.
media.tenor.com
a woman is talking to a man and the words my head is spinning are above her
ALT: a woman is talking to a man and the words my head is spinning are above her
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James Acton @nuclear-jim.bsky.social · 27/06/2025
Iran has ALREADY dug out the tunnels at Isfahan, where most of Iran's highly enriched uranium was stored prior to attacks and PERHAPS during them. (1/2) www.cnn.com/2025/06/27/p...
cnn.com
US’ top general tells lawmakers | CNN Politics
The US military did not use bunker-buster bombs on one of Iran’s largest nuclear sites last weekend because the site is so deep that the bombs likely would not have been effective, the US’ top general...
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JD Menton @jdmenton.bsky.social · 27/06/2025
In @foreignpolicy.com I wrote about Iran and why nuclear uncertainty is bad for regional stability. Unclear diplomatic priorities + backlash against the IAEA w/in Iran are setting us down a dangerous path. @carnegieendowment.org @carnegienpp.bsky.social foreignpolicy.com/2025/06/27/i...
foreignpolicy.com
Don’t Let Iran Become Another Iraq
Nuclear uncertainty is bad for regional stability.
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James Acton @nuclear-jim.bsky.social · 27/06/2025
An analogy. A patient has a tumor behind an abscess. A surgeon operates, skillfully removes the tumor, but predictably ruptures the abscess causing life-threatening sepsis. Afterwards the doctor says, "the abscess wasn't my problem." Do you think the surgery was responsible?
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Mark Fitzpatrick @marktfitz.bsky.social · 27/06/2025
Two days after the recording, I just listened to this, and if I may say so, I don't think I've done a better interview. www.youtube.com/watch?v=VaSA...
youtube.com
Making sense of the '12-day war' between Israel and Iran | Start Here Q&A
YouTube video by Al Jazeera English
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James Acton @nuclear-jim.bsky.social · 27/06/2025
There’s lot of disagreement between friendly intel agencies over the location of Iran’s HEU. But even the best case is… not good. www.nytimes.com/2025/06/26/u...
nytimes.com
Fate of Iran’s Enriched Uranium Is a Mystery
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James Acton @nuclear-jim.bsky.social · 26/06/2025
Telling comments from Sens. Cotton and Graham. It's incredible--and not in a good way--to fight war that's nominally for nonproliferation and end up with several bomb's worth of highly enriched uranium (after further enrichment) left unaccounted for.
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James Acton @nuclear-jim.bsky.social · 26/06/2025
Come and work with us! We're hiring for a new program assistant. Apply by June 30! carnegieendowment.applicantpro.com/jobs/3780781
carnegieendowment.applicantpro.com
Program Assistant, Nuclear Policy Program - Washington, DC
Program Assistant Nuclear Policy Program The Carnegie Endowment for International Peace, a unique global network of policy research centers, is seeking a program assistant to work with scholars in our...
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James Acton @nuclear-jim.bsky.social · 26/06/2025
If Iran left highly enriched uranium in the Isfahan tunnels, it's not "buried beneath rubble." The U.S. didn't try to collapse them with the GBU-57; they're too deep. The U.S. attacked the tunnel entrances, which won't, in itself, prevent recovery. @barakravid.bsky.social x.com/james_acton3...
x.com
(((James Acton))) on X: "If Iran left highly enriched uranium in the Isfahan tunnels, it's not "buried beneath rubble." The U.S. did not even try to collapse those tunnels with the GBU-57; they're too deep. The U.S. did attack the tunnel entrances, which won't in itself, prevent recovery. @BarakRavid https://t.co/lci5S7ml47" / X
If Iran left highly enriched uranium in the Isfahan tunnels, it's not "buried beneath rubble." The U.S. did not even try to collapse those tunnels with the GBU-57; they're too deep. The U.S. did attack the tunnel entrances, which won't in itself, prevent recovery. @BarakRavid https://t.co/lci5S7ml47
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Joe Cirincione @joecirin.bsky.social · 26/06/2025
James’ entire analysis is worth reading but here’s the bottom line: Iran has the means to build a bomb fairly quickly, it now has a strong incentive to do so, and we probably wouldn’t see them doing it.
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James Acton @nuclear-jim.bsky.social · 26/06/2025
How effective were strikes against Iran? U.S. and Israeli officials stress how long it would take Iran to rebuild its previous nuclear program. But there's a MUCH more important issue: How long it would take Iran to get the bomb? For that, a small program would suffice. (1/n)
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James Acton @nuclear-jim.bsky.social · 26/06/2025
Here’s the thing about a “low confidence” assessment. While the agency offering it is acknowledging it could be wrong, it’s still saying that its estimate is more likely to be correct than any alternative.
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JD Menton @jdmenton.bsky.social · 25/06/2025
Some thoughts about Trump's comments today re further nuclear diplomacy with Iran + the Majlis bill to suspend Iran's cooperation with the IAEA (tldr: individually: bad, together: very bad!)
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James Acton @nuclear-jim.bsky.social · 25/06/2025
A single cascade of 174 IR-6 centrifuges could produce a bomb's worth of 90% highly enriched uranium from the 60% enriched material whose location is unknown in 10-20 days. Iran doesn't need to rebuild enrichment facilities on their previous scale to get the bomb.
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Ankit Panda @nktpnd.bsky.social · 25/06/2025
Also, we’ll lose continuity of knowledge on Iran’s activities that’ll be difficult to reestablish without a serious forensic effort.
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James Acton @nuclear-jim.bsky.social · 25/06/2025
If the centrifuges are still operational, that’s a huge deal. If the issue is whether U.S. strikes collapsed the facility vs. “merely”destroyed centrifuges, it’s not.* What's a HUGE deal is that the U.S. thinks most of Iran’s highly enriched uranium survived. www.timesofisrael.com/liveblog_ent...
timesofisrael.com
Results of US strikes on Fordo ‘really not good,’ Israeli sources say
* * *
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James Acton @nuclear-jim.bsky.social · 25/06/2025
This is REALLY bad--and an utterly predictable consequence of military action. Inspectors can't now verify Iran's several bombs worth of highly enriched uranium. This is a MUCH bigger risk than whether the damage done to Fordow meets expectations.
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Secure World Foundation @swfoundation.bsky.social · 25/06/2025
🚀 #SWF launches “Strengthening Strategic Stability at the Nexus of Nuclear & Space Security” with @carnegiecorp.bsky.social + @carnegieendowment.org. Join the Space Boot Camp + Dialogue Series led by @vsamsondc.bsky.social & @nuclear-jim.bsky.social 🔗 swfound.org/space-nuclea...
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James Acton @nuclear-jim.bsky.social · 25/06/2025
You’re totally right. Apologies all round. I’ve deleted and will repost linking to a different tweet.
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